Direct intracapsular development: implications for feeding mechanisms in early juveniles of the gastropod Crepidula dilatata

Abstract

Embryos of Crepidula dilatata develop within egg capsules where they feed on nutritive eggs also deposited within the capsules. Nutritive eggs permit the embryos to develop to a juvenile stage at hatching without passing through a pelagic larval phase. The juveniles enter the local population in posession of a well developed radula and gill filaments covered by lateral, ventral, and dorsal cilia. Initial feeding by the juveniles, employing both the radula and the gill, occurs from the first day of release from the capsule. The radular band of recently hatched snails is functional from the first day in the benthos, and is used for grazing the substrate, driving the mucus cord from the neck-canal to the mouth, and also for extracting mucus balls produced in the food pouch. The gill is active in particle collection from the first day of the free living juvenile, and is noted by the presence of well developed dorsal and ventral ciliature, active in moving mucus and particles over the gill lamellae to form the mucus string at the extreme ends of the gill filaments. The food pouch becomes active two to three days after initiation of production of mucus cords. All the functions associated with feeding, such as the numbers of mucus cords, radular strokes, and mucus balls increase in activity with progressive development of the juveniles.